revert sum agg (#14907)

This pull request reverses the modifications made to the sum/product aggregation target type, ensuring it always produces int64. The changes implemented by  PR [14679](#14679) which led to degraded performance when the aggregation column had an unsigned type, are reverted. Additional details can be found in the issue [14886](#14886).

Authors:
   - Suraj Aralihalli (https://github.com/SurajAralihalli)

Approvers:
   - David Wendt (https://github.com/davidwendt)
   - Nghia Truong (https://github.com/ttnghia)
   - Karthikeyan (https://github.com/karthikeyann)

cpp/include/cudf/detail/aggregation/aggregation.hpp

@@ -1234,12 +1234,12 @@ constexpr bool is_sum_product_agg(aggregation::Kind k)
          (k == aggregation::SUM_OF_SQUARES);
 }
 
-// Summing/Multiplying integers of any type, always use uint64_t for unsigned and int64_t for signed
+// Summing/Multiplying integers of any type, always use int64_t accumulator
 template <typename Source, aggregation::Kind k>
 struct target_type_impl<Source,
                         k,
                         std::enable_if_t<std::is_integral_v<Source> && is_sum_product_agg(k)>> {
-  using type = std::conditional_t<std::is_unsigned_v<Source>, uint64_t, int64_t>;
+  using type = int64_t;
 };
 
 // Summing fixed_point numbers

cpp/tests/groupby/sum_tests.cpp

@@ -28,10 +28,10 @@ using namespace cudf::test::iterators;
 template <typename V>
 struct groupby_sum_test : public cudf::test::BaseFixture {};
 
-using K               = int32_t;
-using supported_types = cudf::test::Concat<
-  cudf::test::Types<int8_t, int16_t, int32_t, int64_t, float, double, uint16_t, uint64_t>,
-  cudf::test::DurationTypes>;
+using K = int32_t;
+using supported_types =
+  cudf::test::Concat<cudf::test::Types<int8_t, int16_t, int32_t, int64_t, float, double>,
+                     cudf::test::DurationTypes>;
 
 TYPED_TEST_SUITE(groupby_sum_test, supported_types);
 
@@ -40,9 +40,6 @@ TYPED_TEST(groupby_sum_test, basic)
   using V = TypeParam;
   using R = cudf::detail::target_type_t<V, cudf::aggregation::SUM>;
 
-  static_assert(std::is_signed_v<R> == std::is_signed_v<V>,
-                "Both Result type and Source type must have same signedness");
-
   cudf::test::fixed_width_column_wrapper<K> keys{1, 2, 3, 1, 2, 2, 1, 3, 3, 2};
   cudf::test::fixed_width_column_wrapper<V> vals{0, 1, 2, 3, 4, 5, 6, 7, 8, 9};